Midas Civil Recommendations 1

[Dwaipayan Sharma]

Hi,

I have been trying to load rate the continuous riveted haunch plate girder with rolled steel floor beams and stringers in Midas Civil. This bridge also has varying depth of girder, the picture of which is attached with this. I haven't used Midas so much. I am only experienced with simple steel beam bridge and prestressed concrete bridge. I am wondering if Midas Civil Expert from this forum can help me with the modeling of this bridge. Is it possible to model this kind of bridge with stringer, floor beam and varying girder depth using Wizard? If yes how? I would really appreciate your help. This load rating project is really important and I am working really hard to get this project done. Your small suggestions would be highly appreciated!

Thanks!

 

[Guest090822]

Tried Midas - hated it. Advice is to use a different program,especially for something this easy.

 

[MIKE_311]

I've never used MIDAS and cant find much on their website. If you are going to model this, makes sure that it will actually run all the ratings you need first. In my experience, its hard to find software to rate these bridges unless they are specially made for load ratings (eg. Brass/BrR). Its rare for a new bridge to have this type of structural system so the software can model it.

You can work the flexural and shear capacity out by hand of each member if you need to. It's running all the rating trucks and permit vehicles in all the necessary combinations that is a chore. If the software wont spit out all the vehicle ratings, why bother.

You might need to build this model yourself in STAAD or some other program that will run all the live load combos and calculate the rating by hand.

 

[pikku14]

Midas is powerful, but my recommendation is to skip over the wizard. Like all in-built wizards, it's really geared up for a very specific arrangement. For the majority of structures that don't fit that template exactly, I'd be completing the model outside of the wizard - all of what you described can be easily modelled in midas or whichever other software you're comfortable with.

 

[Dwaipayan Sharma]

Thank you everyone for your reply. I really appreciate your help!

 

[STrctPono]

I use Midas Civil exclusively as a FEA tool in my office. I guess, technically I am signed up as one of their "Experts" but don't really do anything with that title.

Personally, I love Midas. I find it to be a really powerful program. Maybe not as powerful as Lusas but still really good and a lot cheaper. What I like is that it can still be used as a general FEA program that gives the user lots of freedom to create custom models but is tailored toward bridge design. They have wizards but I NEVER use them. Once you have gotten good with Midas, you can model even a complex bridge in a matter of a few hours....Analysis and Interpretation not included...

I use Midas Civil a ton for analysis, and what I mean by that is that I use it solely to extract force demands from the structure under a particular loading combination. What I don't use it for is design, and by that I mean to calculate capacities of an element. A few exceptions to that rule, 1. Member check for a large steel truss with lots of members (think overhead sign bridge) 2. PT tendon stress loss check 3. Moment-Curvature of element 4. Checking buckling of a member 5. Pushover Design

So, with this being said, I have used the Load Rating features of Midas Civil in the past but I don't anymore. I don't like them and I find other options to be quicker and more transparent.

For your particular problem, unless this bridge is curved or highly skewed, I would use Brass Girder/BrM (as MIKE 311 mentioned). These programs are not hifalutin but they are excellent number crunchers per AASHTO code. They can analyze beams based on stiffness as well, so your haunched beam problem can be correctly analyzed for live load demand and capacity in these programs. Otherwise, you will need to establish your own set of excel spreadsheets (or similar) that can perform the capacity checks based on your analysis from the model. I do this a lot for bridges that are not appropriate for modeling in Brass Girder. I will use Midas Civil to run the analysis, extract all the load demands of consequence and use spreadsheets to run the capacity check and subsequent load rating factor calculation.

See attached. Haunched girder with floor beam deck system. Although concrete not steel... analyzed in Midas Civil several years back. Girders integral with the piers and floor beam system make it so it was not appropriate for Brass Girder.